Papers by Author: Hiroyuki Matsuura

Abstract: Magnetic nanoparticles are widely used in magnetic fluid, magnetic grinding materials, magnetic controllers, magnetic sensors, biomedicine fields and so on. Recently, more and more attentions were focused upon DDS (Drug Delivery System). In this study, Magnetite nanoparticles about 8nm size were synthesized by liquid phase precipitation method. Then the nanoparticles coated with surfactant were dispersed throughout kerosene and inject the solutions into biomaterials. Using strong photon beams in SPring-8 facility, we observed the distribution state and the effect of magnetic field on the behaviour of nanoparticles in biomaterials.

Abstract: Assisted living instruments and medical implants, such as wheelchairs and joint prostheses are usually subjected to biaxial or three-axial stresses instead of uniaxial stress. So, authors already developed a servo biaxial fatigue-testing machine, and clarified about the performance evaluation. Moreover, closed-packed hexagonal lattice metal, such as magnesium and titanium, is frequently used for assisted living instruments or medical implants. In this research, fatigue crack propagation tests of magnesium alloy AZ31B and pure titanium TP340C were conducted under conditions of biaxial and uniaxial loading by using a cruciform specimen in a bi-axial fatigue machine, in order to investigate the effect of non-singular stress cycling on the fatigue crack growth properties ⊿K-da/dN. From these comprehensive experiments, in the magnesium alloy, the re-markable effect was found in the specific biaxial load stress ratio on ⊿K-da/dN relation. When biaxial load stress ratio was 0.5, it turned out that the fatigue crack propagation rate of a magnesium alloy becomes very slow. On the other hand, in the titanium, it was confirmed that there is a little influence of a biaxial load stress ratio on ⊿KⅠ -da/dN relation.

Abstract: The effect of hydrolysis of polycarbonate on tensile behavior were investigated.
The specimens were exposed in a chamber at constant room temperature and water for 300 hours, and measurements were made on the variation of weight and tensile properties. In addition, the increase and decrease of the carbonate part was measured with an ultraviolet spectroscopy. The results are as follows: It was confirmed that it was effective to the examination of the influence of the diffusion of water with an overlay castfilm. It has been understood to the diffusion of water from the surface layer has diffused at the same time by about 6μm, and it has diffused gradually when it is deeper than 6μm. The change in the tensile behavior by the hydrolysis was able to be confirmed by observing the carbonate part of the polycarbonate. It became clear, the break strain has decreased because the carbonate part is taken apart by the hydrolysis. Afterwards, the break strain steadies by constructing a bridge, and the yield stress increases.